1. Field of the Invention
The present invention relates to an image display apparatus applied to liquid crystal projectors and the like.
2. Description of the Related Art
Projection display apparatuses, such as liquid crystal projectors, have been widely used in which image display is performed by applying spatial modulation to the light passing through a spatial light modulation element, and emitting the light thus modulated, and then collecting and projecting the emitted light in response to the electric signal supplied to the spatial light modulation element. The projection display apparatus of this type generally has a lamp and a focusing mirror as a light source, and an illumination optical system for collecting, and admitting the light therefrom into the spatial light modulation element. The light from the spatial light modulation element is projected onto a screen or the like by a projection lens.
As the above-mentioned projection display apparatus, for example, Japanese Unexamined Patent Application Publication No. 2006-3586 has proposed one having a variable iris capable of changing (adjusting) the light quantity of the light from a light source in order to improve sensible contrast feeling. Specifically, when the luminance level of an video signal is high (the image is bright), the iris is opened to make the image look brighter. On the other hand, when the luminance level of an video signal is low (the image is dark), the iris is closed to make the image look darker.